Henson Alternative, an offshoot of the Jim Henson Company, creators of our beloved Muppets and Sesame Street characters, bills their content as “not intended for our youngest viewers.” Don’t expect Elmo or Grover or Big Bird around here, these are Muppets for grown-ups. And they’ve truly swung for their fences, and a hard R-Rating, with their first feature film, “The Happytime Murders,” which is a hard-boiled detective neo-noir film starring these fuzzy puppety friends alongside human actors. Unfortunately, some mildly-amusing ideas shouldn’t be full-length feature films and “The Happytime Murders” falls victim to that.

Directed by Brian Henson, and written by Todd Berger and Dee Austin Robertson, the entire conceit of “The Happytime Murders” is: Puppets Behaving Badly. It’s just that there’s nothing else to the joke. That’s it. And frankly, that joke’s been done before. The film pushes the levels of decency and taste into the gutter, then pushes it further, and that’s supposed to be funny. Because puppets! Clearly it’s inspired by the likes of the Broadway musical “Avenue Q,” and “Team America: World Police,” which got away with explicit sex and crude body humor because the protagonists were marionettes. “The Happytime Murders” is just another retread of that concept.

Bill Barretta voices the hero, Phil Philips, a puppet private investigator and former detective living in L.A., where puppets are equal, but discriminated against. Their poor treatment is a racial metaphor that never quite takes off. He’s hired by a comely female puppet, Sandra White (Dorien Davies), asking him to look into a series of threatening blackmail letters. In his search, he becomes witness to a brutal murder in a porn shop, which turns into the systemic execution of a group of puppets who starred on an ’80s TV show, “The Happytime Gang,” including his brother, Larry. He runs into his old police detective partner, Connie Edwards (Melissa McCarthy) and the two are soon begrudgingly working the case together.

McCarthy does everything in her power to propel this project forward, but no amount of physical comedy can erase the fact that this movie is simply D.O.A. The humor relies on graphic depictions of puppet violence, puppets doing drugs (sugar, rather), gambling, having sex, beating people up — all things you’d never expect to see a fuzzy puppet friend do. Despite the best efforts of McCarthy, and a winsome Maya Rudolph as Phil’s 40s-style secretary Bubbles, “The Happytime Murders” is more like the “Boringtime Slog.” It’s only 90 minutes, but this unoriginal and crude dreck isn’t even worth your hour and a half.

MOVIE REVIEW

“The Happytime Murders”

Grade: D

Starring Melissa McCarthy, Bill Barretta and Joel McHale. Directed by Brian Henson.

Rated R for strong crude and sexual content and language throughout, and some drug material. Check listings for theaters. 1 hour, 31 minutes.

Bottom line: Retread of the concept of Puppets Behaving Badly